<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>if标签</title>
</head>
<body>
    {% if num < 10 %}
        <p>好好学习</p>
    {% elif num < 20 %}
        <p>天天向上</p>
    {% else %}
        <p>好好吃饭</p>
    {% endif %}
</body>
</html>